1. Field of the Invention
This invention relates to means for blocking fluid flow in a flexible conduit, particularly in a conduit connecting two or more flexible containers as in a multiple blood bag system.
2. Prior Art
A variety of means have been developed for blocking the flow of fluid from one blood bag to another through interconnecting tubing until such time it is desired to transfer the fluid from one bag to another. Generally this has involved a valve system wherein a membrane closing fluid flow, which is located in the interconnecting tubing, is pierced by a cannula as shown in U.S. Pat. Nos. 3,110,308, and 3,685,795, or by a spike member such as in U.S. Pat. No. 4,195,632, to allow fluid to be transferred. It is also possible to block the flow of a fluid by the use of an external slide clamp such as those disclosed in U.S. Pat. Nos. 3,064,647 and 3,078,847.
However, there are several disadvantages in the use of such blocking means. Blood bag systems have an anticoagulant in the primary or donor bag for the purpose of preventing coagulation of blood collected therein. To render the system sterile, blood bags must be subjected to a sterilization cycle involving exposure to steam at about 115.degree. C. for about 50 minutes. It has been found that the inner surfaces of conventional vinyl tubing become fused together at the point where the tubing is clamped as a result of heat sterilization. Fluid flow between the donor bag and a second or satellite bag is therefore blocked even after removal of the clamp. Even if the walls of the tubing do not fuse together, the slide clamp sometimes is ineffective in completely closing the tubing and leakage occurs. During heat sterilization, the tubing softens and can sometimes be cut by sharp edges of the clamp.
Other means for blocking flow through flexible tubing are disclosed in U.S. Pat. Nos. 2,895,475, 2,995,334, and 3,103,335. In each instance, the tubing is closed off by bending the tubing back on itself and applying a restraining device of some sort to maintain the tubing in this position. The tubing is thus pinched off at the folding point. In U.S. Pat. No. 2,922,613, a malleable metal pipe placed around the tubing can be bent to approximately 90.degree. at which point the tubing becomes pinched off. Although these means are simple and easy to use to block fluid flow in flexible tubing, the problem of fusion of tubing walls as a consequence of heat sterilization would not be avoided by the use of such devices.